Mechanism of Corrosion Product Growth on Nickel Aluminum Bronze /10 Ammonia-90 Seawater Interface: Effect of Applied External Stress
Abstract
This investigation was undertaken to develop a corrosion process model based on the chemical reaction kinetics in materials. A mathematical model relating the process parameter (viz. the weight change, the measured open circuit potentials (versus SCE) and the change in the structure of the material) and the reaction time was developed. This model was tested with nickel aluminum bronze (NAB) samples in 10 NH4OH 90 seawater solution, and the kinetics parameters such as the rate constant and the order of reaction, were determined. In addition, the effect of applied external stress on the corrosion process was also investigated. The nickel aluminum bronze (NAB) samples were exposed to 10 NH4OH -90 seawater solution for up to 46days. In addition, some samples were subjected to the continuous application of 7.5 ksi and 15 ksi stress. The weight change was measured on all samples. Similarly the structure of the corroded sample surface was determined from their x-ray diffraction patterns. The weight change data and the structural analysis based information were fed into the reaction kinetics model and the oxide characteristics were determined. Results suggest that the kinetic parameter such as the order of reaction for the corrosion process that was predicted by feeding all three sets of data into the model indicates that the corrosion of NAB in 10 NH4OH - 90 seawater is a diffusion controlled process. The kinetics of the fast reaction stage is controlled by the availability of NAB sample surface for corrosion. The slow chemical reaction stage is very complex. The complexity is perhaps due to the nucleation and growth of complex and mixed oxides/hydroxides. During the corrosion process the rate of corrosion of iron is the highest and the corrosion of the nickel is the slowest. The rate of corrosion increases with an increase in the applied stress.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2008
- Accession Number
- AD1068214
Entities
People
- A. S. Rao
Organizations
- Naval Surface Warfare Center Carderock Division